The present invention relates to electrical moisture testers for measuring the moisture content of shelled corn in a combine.
Electrical moisture testers for measuring the moisture content of vegetable matter, and in particular grains, are well known in the art. Most moisture testers operate on the principal that the electrical properties (namely, resistance or resistivity) of vegetable matter vary with the moisture content of the matter.
Some moisture testers, especially those for measuring grains, are designed to take bulk measurements after the grain or other crop has been harvested and is in storage. Such bulk measuring devices are not particularly useful or convenient in helping a farmer determine when to harvest the crop, or a seed corn company in determining "dry down" time of a new hybrid seed under development.
It is known that the relationship between cob moisture and the moisture content of corn kernels on the cob varies substantially with different corn genotypes, different moisture levels, and even with the weather. Thus, cob moisture cannot generally be correlated with corn kernel moisture. It is also known that the moisture content of the husk can influence the value of the moisture reading obtained, especially when a test is conducted in the field while the ear is still on the plant.
A moisture tester designed to estimate the moisture content of corn kernels on the cob is disclosed in an article entitled An Electronic Probe For Estimating Ear Moisture Content of Maize (Kang, et al, Crop Science, Vol. 18, Nov.-Dec. 1978, pp. 1083-1084). That device uses a pair of spaced needle-shaped conductors which are applied to penetrate the husk, kernels and cob. The moisture meter then signals the relative magnitude of the electrical resistance of the cob, kernels and husk in contact with the needle conductors.
U.S. Pat. No. 4,954,783, issued Sep. 4, 1990 in the name of the present inventor, discloses an apparatus and method for testing the moisture content of corn kernels on an ear of corn. The apparatus includes an ear cradle, a pair of electrode blades, and a circuit for measuring a moisture-dependent electrical property of the corn kernels. The major advantages of this device are that it is versatile, highly portable, reliable, accurate and inexpensive. The present invention contemplates even greater versatility and convenience for the farmer using my device.
It is important for the farmer to know the moisture content of corn at harvest. It has been estimated that the cost of drying corn is reduced by approximately 21/2.cent. per bushel per percentage point of moisture content down to approximately 15%. Thus, the ability to accurately measure corn moisture content allows the farmer to determine the optimum time for harvest as well as to select which of different varieties of corn to harvest depending upon moisture content. Once the farmer has made his preliminary determination to harvest a field, he has no way to assure himself that his pre-harvest tests were reliable unless, after harvesting the first few bushels, he takes a sample back to his shop for bulk testing (requiring another instrument).